This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-167166, filed Jun. 14, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an optical pickup for recording on and reproducing information from an optical disk.
As an example of a thin-type optical pickup, there is an optical pickup including a floating objective lens, which is lifted off an optical disk by means of air currents. Since the floating objective lens is very small, a small-diameter light beam may be used, so that the optical pickup using the floating objective lens can be thinned.
An example of an optical pickup using a floating objective lens is described in Jpn. Pat. Appln. KOKAI Publication No. 5-73946. This optical pickup comprises a floating objective lens adapted to be lifted off by means of air currents produced as an optical disk rotates, a light source for emitting a light beam, and a reflecting prism, so-called riser mirror, for deflecting the light beam at 90xc2x0 to direct it to the objective lens. The optical pickup further comprises a relay lens system including two lenses and interposed between the light source and the riser mirror. The lens on the light source side is movable at right angles to the optical axis for tracking control; while the lens on the riser mirror side is movable along the optical axis for focus control.
When the lens for tracking control is moved at right angles to the optical axis, its focal point is deviated from the optical axis. Accordingly, the light beam projected from this lens has an inclination to the optical axis. After it is reflected by the riser mirror, therefore, the light beam falls on the objective lens at an angle to the optical axis of the lens. In consequence, the light beam is focused on the optical disk at a position, which is off the optical axis of the objective lens. Tracking control is carried out in this manner.
The light beam thus inclined with respect to the optical axis for tracking control recedes from the optical axis on departing from the lens for tracking control. Accordingly, the riser mirror should have a certain measure of area, and the objective lens is expected to have a corresponding effective diameter.
These requirements entail an increase in size of the riser mirror and the objective lens and constitute a hindrance to the reduction in thickness of the optical pickup.
The present invention has been contrived in consideration of these circumstances, and its object is to provide a thin-type optical pickup in which a riser mirror and an objective lens are reduced in size.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.